1. Field of the Invention
The present invention relates to the production of higher alcohols. In particular the invention is a process for the preparation of these alcohols by conversion of carbon monoxide and hydrogen containing synthesis gas admixed with lower alcohols in presence of one or more catalysts being active in the conversion of carbon monoxide and hydrogen to higher alcohols.
2. Description of the Related Art
It is known that higher alcohols and other oxygenates are formed as by-product in the catalytic methanol synthesis from synthesis gas.
It is also known that higher alcohol products can be produced directly from synthesis gas.
US patent application No. 2009/0018371 discloses a method for the producing alcohols from synthesis gas. The synthesis gas is in a first step partially converted to methanol in presence of a first catalyst and in a second step methanol is converted with a second amount of synthesis gas to a product comprising C2-C4 alcohols in presence of a second catalyst. The second amount of synthesis gas can include unreacted synthesis gas from the first step.
The alcohol synthesis requires a high concentration of carbon monoxide in the synthesis gas. A useful synthesis gas has a H2/CO ratio of at least 0.4. The synthesis gas for the higher alcohol synthesis is prepared by the well-known steam reforming process of liquid or gaseous hydrocarbons or by means of gasification carbonaceous material, like coal, heavy oil, petroleum coke and bio mass.
Hydrogen and carbon monoxide react to produce methanol:                Syngas to methanol,CO+2H2⇄CH3OH        
The methanol reacts with the syngas and a chain growth to higher alcohols is initiated, according to the following reaction scheme:                Chain growth by reaction with synthesis gas,CH3OH+CO+2H2⇄C2H5OH+H2OC2H5OH+CO+2H2⇄C3H7OH+H2OC3H7OH+CO+2H2⇄C4H9OH+H2Oetc.        
It has been found that addition of lower alcohols to the synthesis gas results in a drastic increase in the yield of higher alcohols when compared to the conventional methanol synthesis gas.
As used hereinbefore and in the following description and the claims, the term “lower alcohols” refers to alcohols present in synthesis gas for use in the higher alcohol synthesis and the term “higher alcohols” refers to alcohols higher than the alcohols in the alcohol synthesis gas.
The alcohols obviously couple together and form higher alcohols:                Aldol coupling,CH3OH+C2H5OH⇄C3H7OH+H2OC2H5OH+C3H7OH⇄C5H11OH+H2Oetc.        